The wrench is widely used in daily life, and is generally used to tighten or release a fastener, such as a nut with a bolt. Common wrenches are categorized into the open-end wrench and the ratchet wrench. Generally, a fastener can be arranged in the open-end wrench through the opening on one side of the wrench. During the tightening or releasing operation, the wrench needs to be removed from the fastener after rotating the fastener a relatively small angle, and then the wrench is positioned at another angle on the fastener so as to continue to rotate the fastener. This process needs to be repeated several times until the fastener is completely tightened or released, thus the operation is not convenient. Moreover, the open-end wrench cannot be used in some narrow spaces. As for the ratchet wrench, the entrance portion thereof is generally configured as a closed structure, and then the ratchet wrench needs to surround the fastener from the upper portion or the lower portion thereof in order to tighten or release the fastener, thus the operation is also not convenient.
To enhance the working efficiency and the convenience of the fastening operation, there are some electrical wrenches in the market. However, these known electrical wrenches are seen to have limited usefulness owing to the manner in which they are constructed.